But there's another way to help the climate. A recent study from Lund University in Sweden shows that the biggest way to reduce climate change is to have fewer children.

"I knew this was a sensitive topic to bring up," says study co-author Kimberly Nicholas on NPR's Morning Edition. "Certainly it's not my place as a scientist to dictate choices for other people. But I do think it is my place to do the analysis and report it fairly."

The study concludes that four high-impact ways to reduce CO2 gas emissions include having fewer children, living without a car, avoiding airplane travel and eating a vegetarian diet.

By the numbers, any of these lifestyle changes drastically reduces carbon emissions compared to more common practices like recycling, using energy-efficient light bulbs and line-drying clothes.

having one fewer child (an average for developed countries of 58.6 metric ton CO2-equivalent (tCO2e) emission reductions per year;